The present invention relates to a gasification reactor comprising a gasifier in a tubular gastight wall with a lower end opening into an aqueous slag collection bath, wherein the gastight wall is arranged within a pressure vessel.
Gasification reactors can for instance be used for the production of synthesis gas by partial combustion of a carbonaceous feed, such as pulverized coal, oil, biomass, gas or any other type of carbonaceous feed. Some gasification reactor types only have a discharge opening at their lower end for discharging syngas via the aqueous slag collection bath via a discharge, often referred to as dip tube. Due to the pressure build-up in the gasifier freshly produced synthesis gas is forced to flow down through the slag collection bath around the lower edge of the dip tube to be recollected in the annular space between the gasifier wall and the pressure vessel wall. This way the water in the slag collection bath cleans and cools the synthesis gas.
In order to reduce thermal stresses the gasifier wall is typically cooled and can for instance be formed by parallel tubular lines confining channels for a coolant medium such as water. These tubular lines are interconnected to form a gastight wall structure, e.g., in a tube-fin-tube arrangement. These gasifier walls are subjected to loads induced by the high operational pressures within the gasifier. The pressure within the gasifier can be as high as, e.g., 20-80 bar. To reduce pressure induced mechanical loads in the gasifier wall, it is desired to balance the internal gasifier pressure with the pressure in the surrounding annular space between the gasifier and the pressure vessel. This requires that the pressure within the annular space is kept about as high as the pressure within the gasifier. On the other hand, synthesis gas blown from the gasifier into the slag collection bath should be able to bubble up within the annular space between the dip tube and the pressure vessel. This requires that the pressure in the annular space above the slag collection bath should be substantially less than the pressure within the gasifier. This is usually achieved by separating the annular space into an upper section surrounding the gasifier and a lower section above the slag collection bath by means of an annular seal. Such a single seal is simultaneously exposed to a permanent high pressure from the upper section and to a lower pressure from the lower section, which fluctuates with a high frequency when synthesis gas bubbles up from the slag collection bath. The accumulated loading pattern can lead to early failure of the seal.
It is an object of the invention to provide a robust and reliable separation of the upper and lower sections of the annular space between the gasifier wall and the surrounding pressure vessel.